UC Davis researchers aid effort to sequence the complex wheat genome

The bread wheat genome is especially complex because bread wheat originated from three ancient grass species

December 11, 2012

Posted by Pat Bailey

Intent on developing wheat varieties with higher yields and enhanced nutritional content, researchers at UC Davis have teamed up with scientists at nine other institutions in an attempt to sequence the wheat genome.

Intent on developing wheat varieties with higher yields and enhanced nutritional content, researchers at the University of California, Davis, have teamed up with scientists at nine other institutions in an attempt to sequence the wheat genome.

Results from that endeavor, led by researchers at the U.K.-based Biotechnology and Biological Sciences Research Council, will be reported Nov. 29 in the journal Nature.

"This work moves us one step closer to a comprehensive and highly detailed genome sequence for bread wheat, which along with rice and maize is one of the three pillars on which the global food supply rests," said Jan Dvorak, professor of plant sciences at UC Davis and a study co-author.

"The world's population is projected to grow from 7 billion to 9 billion by 2050," he said. "It is clear that, with no new farmable land available to bring into cultivation, we must develop higher-yielding varieties of these three cereals to meet the growing global demand for food."

The bread wheat genome is especially complex because bread wheat originated from three ancient grass species. Its genome is, therefore, a composite of three genomes -- and is five times the size of the human genome.

Wheat geneticists have historically designated the genomes of those parent grasses as the A, B and D genomes, each containing a similar set of genes. As a result, most bread wheat genes exist in triplicate.

To aid the sequence assembly of bread wheat, Dvorak and the UC Davis researchers have worked with scientists at the U.S. Department of Agriculture's Agricultural Research Service and with scientists at two other U.S. institutions on sequencing of the genome of the parent species Aegilops tauschii -- the source of the bread wheat D genome.

The U.S. team shared the Aegilops tauschii sequences with the British team, which was assembling all three of the wheat A, B and D genomes.

Comparing the Aegilops tauschii sequence with modern wheat allows researchers to assess genomic changes that have taken place in bread wheat since its origin approximately 8,000 years ago.

In the study reported in Nature, the researchers used the whole genome "shotgun sequencing" approach, which generates billions of random genome sequence "reads" and then pieces them together. The results provide information about the DNA making up wheat genes that will help wheat breeders develop hardier varieties by linking genes to key traits, such as disease resistance and drought tolerance.

"This sequencing effort has yielded important information that will accelerate wheat genetics and breeding and help us better understand wheat evolution," Dvorak said. "It cannot be overemphasized, however, that this is just one step in the global effort to produce a high-quality draft of the bread wheat genome sequence."

He said completion of such a high-quality genome sequence for bread wheat is still a few years away and will require broad international collaboration to complete.

Other members of the UC Davis team included Ming-Cheng Luo, Patrick E. McGuire and Frank M. You, all of the Department of Plant Sciences. The USDA team also included two UC Davis research affiliates -- Olin D. Anderson and Yong Gu -- at the USDA Agricultural Research Service Western Regional Research Center in Albany, Calif.

The other collaborating institutions were Kansas State University; Cold Spring Harbor Laboratory, New York; University of Liverpool; University of Bristol; John Innes Centre; and European Bioinformatics Institute.

Funding for the study was provided by the Biotechnology and Biological Sciences Research Council of England, the USDA's National Institute of Food and Agriculture, The Royal Society, the German Ministry of Education and Research, and the National Science Foundation.